Antenna with cosecant squared pattern are special designed for air- surveillance radar sets. These permit an adapted distribution of the radiation in the beam. a fan beam. Figure Vertical projection of the radiation pattern of an antenna with cosecant squared characteristic, the blue graph shows the theoretically form, . This paper deals with the analysis and proper design of parabolic reflector antennas to obtain pencil beam, cosecant-squared and inverse cosecant- squared.
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It also illustrates that: Design Frequency The frequency of the antenna. The same basic concept soon found many roles.
Views Read Edit View history. See Raemer, Harold R.
Azimuth Beamwidth The full width of the beam in the x-y plane of the beam coordinate system. To counteract this, the scanning antenna was re-aimed so that it was pointed almost directly forward, thereby sending most of the radar energy at low angles relative to the aircraft, thereby increasing the energy available at long range. Vertical projection of the radiation pattern of an antenna with cosecant squared characteristic. According to definition mentioned above the height also shall be constant.
Cosecant Squared Pattern Antennas
However, what does this term have to do with our antenna? A cosecant squared antennasometimes known as a constant height patternis a modified form of parabolic reflector used in some radar systems.
This gives in near range an additional gain required for constant echo strength after sensitivity time control. The part of the rays which falls to the less bent area in the top is reflected up now.
The angle 1 in the above equation and illustration.
Alpha M Angle The angle m in the above equation and zquared. The name refers to cosecsnt fact that the amount of energy returned from a target drops off with the square of the cosecant of the angle between the radar and the target. For an antenna linked to a receiver, transmitter, or radar, the Antenna Design Frequency value gets overridden by the Frequency value set on the Model Specs tab for the transmitter or receiver, and the on the Transmitter Specs tab for the Radar.
You can specify the following parameters: This antenna uses a polar coordinate system. Cosecant-squared pattern achieved by displacing the reflector surface from the original parabolic shape.
Without correction, this produced a display where the ground under the aircraft was very bright on the cathode ray tube squaref, while the terrain at longer distances was almost invisible. The ground directly below the aircraft is at a distance equal to the aircraft’s altitude, which produces the strongest signal. For ground-based radars, the same antenba could be used to provide scanning at high angles above the station while still sending most of the energy towards low angles to detect aircraft at long range as they rose above the radar horizon.
Antenna with Cosecant Squared Pattern Cosecant squared pattern.
Cosecant squared antenna
CRC Presspp. The angle m in the above equation and illustration.
The cosecant squared pattern isn’t restricted to parabolic reflectors. The angle 2 in the above equation and illustration. Retrieved from ” https: It is shaped to send more radio energy in certain directions in order to smooth out the reception pattern of objects as their range changes in relation to the radar. Antennae with constant height pattern or cosecant squared pattern are special designed for air-surveillance radar sets.
A possibility consists in lower bending of the top of the reflector. Open topic with navigation. At use of several receiving channels a height allocation also can be carried out. Main-lobe Gain dB The main lobe gain of the antenna pattern. The terrain at further distances returns much less signal due to the radar equation. In the practice a cosecant squared pattern can be achieved by a deformation of a parabolic reflector.